The present invention relates to a pump and to a receptacle containing a liquid, e.g. a cosmetic or care cream, and fitted with such a pump.
French patent FR-B-2 728 809 discloses a pump having a pushbutton movably mounted on a support secured to the receptacle containing the substance to be dispensed, the pushbutton having a central duct provided with a radial opening at its bottom end, the support defining a variable-volume pump chamber around said central duct. A diaphragm made of elastomer material is mounted on the support. The diaphragm has a central portion in the form of a sleeve that is open at its top end and closed at its bottom end. The central duct of the pushbutton is inserted in the diaphragm via one end until it bears against the end wall of the central portion of the diaphragm.
The above diaphragm acts as a spring for returning the pushbutton to its initial position after dispensing a quantity of substance.
It also acts as a delivery valve.
During the return movement of the pushbutton, the diaphragm presses against the central duct and isolates the pump chamber from the radial opening in the central duct so as to prevent air returning into the pump chamber.
Such a pump has the advantage of requiring only a small number of parts and thus of being suitable for manufacture at relatively low cost.
Nevertheless, that known pump does not provide full satisfaction.
In particular, the pump can be difficult to prime and under certain conditions the substance flows with difficulty between the central duct of the pushbutton and the diaphragm, thereby causing the pushbutton to jam.
The invention seeks to further improve a pump of the type comprising a moving member mounted to move relative to a support, the moving member having a central duct in which the substance to be dispensed penetrates via at least one opening, the support co-operating with the moving member to define a variable-volume pump chamber around said central duct, the pump having a diaphragm held by retaining means on the support, the diaphragm having a central portion in which one end of said central duct is inserted, the diaphragm having a valve-forming portion arranged to isolate the pump chamber from said opening(s) of the central duct while the volume of the pump chamber is increasing and the substance is being sucked into the pump chamber, the diaphragm also bearing against the moving member in such a manner that movement of the moving member to dispense the substance causes the diaphragm to be stretched elastically.
The new pump of the invention has means suitable, during movement of the moving member for dispensing the substance, for minimizing the stretching of the valve-forming portion of said diaphragm. In a preferred embodiment, the central portion of the diaphragm has first engagement means arranged to co-operate with second engagement means secured to the central duct, the second engagement means being spaced apart from the end of the duct which is inserted in the central portion of the diaphragm.
By the invention, the end of the central duct bears only lightly or not at all against the end wall of the central portion of the diaphragm when the moving member is moved to dispense the substance, unlike the pump described in French patent 2 728 809 in which the diaphragm is stretched elastically, specifically by the fact that the central duct of the pushbutton bears directly against the end wall of the sleeve-shaped central portion of the diaphragm.
Advantageously, the portion of the diaphragm extending between the retaining means of the support and the engagement zone of the central duct performs a spring function only.
Also advantageously, the portion of the valve-forming diaphragm that is arranged to isolate the pump chamber from the opening(s) of the central duct lies outside the portion of the diaphragm that extends between the zone for fixing on the support and the zone for engagement on the central duct.
In the invention, the central portion of the diaphragm comes to bear against the central duct at a location that is remote from the end thereof, thereby reducing the mechanical stresses to which the end wall of the central portion of the diaphragm is subjected.
In addition, because the end wall of the central portion of the diaphragm is subjected to less stress, it becomes easier to enable the diaphragm to perform its delivery valve function, i.e. to enable it to isolate the pump chamber from the opening(s) of the central duct while the volume of the pump chamber is increasing and substance is being sucked into the chamber. The bottom portion of the central portion of the diaphragm can deform more easily in a direction perpendicular to the direction in which the top portion of the central portion of the diaphragm is stretched because it is subjected to less axial stress, and this makes it easier to pass the substance that is to be dispensed.
In a particular embodiment, the first engagement means of the diaphragm form a channel that is open in the direction facing away from the end wall of the central portion of the diaphragm, and the second engagement means comprise an engagement skirt directed towards the end of the central duct.
Still in a particular embodiment, the above-mentioned channel is formed between two concentric tubular walls respectively constituting the bottom portion and the top portion of the central portion of the diaphragm, that overlap in part, and that are united by a transverse wall constituting the web of said channel.
Advantageously, the tubular wall forming the bottom portion of the central portion of the diaphragm has at least one and preferably a plurality of axial slots in its radially inner surface.
These axial channels facilitate flow of the substance while it is being dispensed.
Advantageously, the above-mentioned axial slots extend downwards from the top end of the tubular wall forming the bottom portion of the central portion of the diaphragm to perceptibly beneath the above-mentioned transverse wall.
Advantageously, the diaphragm is arranged to isolate the pump chamber from the opening(s) of the central duct by causing an annular region to bear in leakproof manner against a zone of the central duct situated beneath the second engagement means.
This zone of the central duct against which the diaphragm presses while the volume of the pump chamber is increasing and the substance is being sucked into the chamber is advantageously defined by an annular bead. The diaphragm co-operates with the central duct to provide annular clearance on either side of said bead, thereby making it easier for the substance to flow while it is being dispensed.
In a particular embodiment, the bottom portion of the central duct has at least one radial opening.
In a variant, the bottom portion of the central duct does not have any radial opening, which makes it easier to manufacture.
Advantageously, the second engagement means of the central duct are constituted by the ends of thicker portions of the central duct, said thicker portions leaving slots between one another enabling the substance to pass towards the opening(s) of the central duct.
Advantageously, the diaphragm has a flexible lip suitable firstly for isolating the pump chamber from the source of substance while the volume of the pump chamber is decreasing, and secondly for enabling the substance to penetrate into the pump chamber while the volume thereof is increasing.
This flexible lip acts somewhat like an intake valve.
Furthermore, the flexible lip is advantageously connected to the central portion of the diaphragm so as to form a downwardly open annular channel, and the retaining means are constituted by the end of an inner skirt coming to bear against the web of said channel so as to retain the diaphragm when the moving member is moved downwards in order to decrease the volume of the pump chamber.
The above-mentioned inner skirt advantageously has openings at its top end, the height of the openings being less than the height of the flexible lip, said openings enabling the substance to reach the pump chamber while its volume is increasing, and while the flexible lip is spaced apart from the inner skirt under the effect of thrust from the substance flowing towards the pump chamber.
In a particular embodiment, the flexible lip is of thickness that increases going towards the top end of the diaphragm.
Still in a particular embodiment, the central portion of the diaphragm is connected at its top end to an annular portion of width and thickness selected in such a manner as to improve retention of the diaphragm while said central portion is being stretched.
Advantageously, the support includes sealing means bearing in leakproof manner against the tubular skirt of the moving member, said tubular skirt being downwardly open and extending concentrically around the central duct, said tubular skirt also defining the radially outer wall of the pump chamber.
Advantageously, when the pump is at rest, the portion of the diaphragm that extends axially between the retaining means and the engagement means of the duct is under tension, which enables the moving member to be maintained in abutment in its high position.
The invention also provides a receptacle fitted with a pump as defined above.